Katherine Heigl has relished her experience as a mum of a newborn baby, despite feeling like a "zombie" for the first few weeks.The actress and husband Josh Kelley adopted a second daughter, named Adalaide, earlier this year (12) as a sister for their other adopted girl Naleigh, three. Their first child was nine months old when she was welcomed into the family, while little Adalaide was a newborn - and Heigl admits it was a completely different aspect of motherhood. She tells entertainment news website People.com, "I had never had a newborn before. I didn't really have that experience. So it's all been new. I was prepared for the nights and having to get up and all of that. But the beauty of it is it's really only a few months of your life that you're walking around like a zombie because you haven't slept. "I think it's far more chaotic than I anticipated. And I think every parent probably says that and every parent tries to warn new parents about it. And we all go, 'Pish posh, it's going to be fine. What's one more?'" And the star reveals Naleigh is also enjoying her new role as a big sister - despite a rocky start. She adds, "Naleigh was super excited about having a new baby sister - until she arrived. Then she was a little hesitant about whether or not she wanted her to stay. And then she became her little protector and is taking on the role of big sister very seriously."